1. Field of the Invention
The present invention relates to an image processing apparatus. More particularly, the present invention relates to an image processing apparatus for restoring a degraded image obtained by an image capturing device (such as a digital camera) to provide an image close to its original image.
2. Description of the Related Art
An image obtained by an image capturing device such as a digital camera (hereinafter referred to as a captured image) is degraded due to out-of-focus photographing, camera-shake or aberration or the like. In typical image restoring processing, iterative calculations are performed for removing the degradation and restoring the captured image to an image close to its original image.
In the iterative calculations, a residual (pixel output difference before and after the iterative calculation) may be computed in each time of iteration and convergence judgment may be carried out until the calculation result becomes below a predetermined threshold value. In such a case, the number of iterations may sometimes be excessive or insufficient for some images so that noises are generated, which hinders desired image restoration. Although a method of setting the number of iterations in advance is proposed by Japanese Patent Application Laid-Open No. 06-54172 for example, it is not yet known based on what the number of iterations should be determined for realizing highly accurate image restoration.
An object of the present invention, which is conceived under the circumstances described above, is to provide an apparatus capable of performing highly accurate image restoration without being influenced by an image.